1. Field of the Invention
The present invention relates to an abrasive dresser for abrading a flat rotatable polishing disc of a chemical-mechanical polisher which supplies a chemical polishing agent to the surface of the polishing disc to polish the surface of an article such as a wafer on top of the polishing disc. In particular the invention relates to an abrasive dresser for a polishing disc of a chemical-mechanical polisher, designed so that the portion of contact with the polishing disc of the chemical-mechanical polisher becomes surface contact, thereby enabling a reduction in wear during use and an increase in life, together with an increase in the efficiency of abrading the polishing disc.
2. Description of the Related Art
Recently, with the manufacture of semiconductor products such as integrated circuits, circuit integration has increased in response to the requirement for increased integrated circuit capacity, and with this there has been a thinning of the insulation film between circuit layers. To meet this requirement, a technique has been adopted for manufacturing integrated circuits including, as shown in FIG. 7, forming on a silicon substrate 1, wiring grooves 2 in conformity to a wiring pattern, and then under this condition, forming a metal layer 3 such as an aluminum layer over the whole surface of the silicon substrate 1. After this, a flat wiring pattern is formed by polishing away the metal layer 3 so that only the metal layer 3 inside the wiring grooves 2 remains. A plurality of the wiring patterns are multi-layered.
FIG. 8 is a cross-sectional view showing a polishing disc 4 of a chemical-mechanical polisher (referred to hereunder as a CMP) which is used, in the manufacture of the abovementioned integrated circuit, at the time of polishing the metal layer 3 for the wiring, which is formed over the whole surface of the silicon substrate 1. As shown in FIG. 8, the polishing disc 4 is made by affixing a flat polishing pad 6 onto a flat disc base 5. A fine abrasive material is mixed with a chemical polishing agent such as an acid, and this is supplied to the surface of the polishing pad 6 of the polishing disc 4. Then by rotating the polishing disc 4, and contacting the metal layer 3 of the silicon substrate 1 which is retained on a retainer 7, against the surface of the polishing pad 6, the metal layer 3 is polished away by the chemical polishing agent and the abrasive material.
Since the polishing pad 6 of the polishing disc 4 is also worn at the time of polishing away the metal layer 3 so that the flatness of the polishing pad 6 cannot be maintained, an abrading apparatus for abrading the polishing pad 6 is incorporated into the CMP. The polishing pad 6 is thus abraded with an abrasive dresser of the abrading apparatus.
FIG. 9 is a cross-sectional view showing a conventional abrasive dresser 8. The abrasive dresser 8 comprises for example, an outer peripheral portion of a circular flat disc base member 9 protruding upwards with a predetermined width, and an abrasive surface 11 formed by substantially uniformly distributing and affixing an abrasive grit such as diamond grit to the surface of the upward protruding portion 10.
As shown in FIG. 10, the abrasive dresser 8 is retained by a retainer 12. By rotating the polishing disc 4 and contacting the abrasive surface 11 of the abrasive dresser 8 which is retained by the retainer 12, from above against the surface of the polishing pad 6, the surface of the polishing pad 6 of the polishing disc 4 is abraded. At this time, when an additional load is applied in the direction of the arrow P to the central portion of the retainer 12 so that the abrasive surface 11 of the abrasive dresser 8 pushes against the polishing pad 6 of the polishing disc 4 from above, then under the pressing force of the abrasive surface 11 the polishing pad 6 deforms to a slightly sunken shape due to its resilience. Then, as a result of the abrading of the polishing pad 6, the flatness of the surface of the polishing pad 6 is maintained, and cleaning of the pad surface is also effected.
With this conventional abrasive dresser 8 however, since as shown in FIG. 9 the sectional shape of the abrasive surface 11 is formed as a flat surface, then when as shown in FIG. 10 the abrasive surface 11 of the abrasive dresser 8 is pressed from above against the polishing pad 6 of the polishing disc 4, the polishing pad 6 is pressed by the overall surface of the abrasive surface 11 which is formed in a doughnut shape with a predetermined width at the outer peripheral portion of the base member 9. However due to this pressing, the deformation to a sunken shape of the polishing pad 6 becomes greatest at the outermost peripheral portion of the abrasive surface 11. Consequently, the contact pressure of the abrasive surface 11 on the polishing pad 6 becomes greatest at the outermost peripheral portion, effectively resulting in a linear contact condition due to the circle, that is the contour of the outermost peripheral portion.
Due to this, then only the abrasive grit distributed over and affixed to the outermost peripheral portion of the abrasive surface 11 is contacted strongly against the polishing pad 6 to give abrasion, and hence only this abrasive grit is rapidly worn. On the other hand, the abrasive grit distributed over and affixed to the inner peripheral portion of the abrasive surface 11 does not have sufficient contact pressure against the polishing pad 6, and hence this cannot effectively contribute to the abrasion of the polishing pad 6. Consequently, the resultant abrasive dresser 8 where the abrasive grit affixed to the outermost peripheral portion of the abrasive surface 11 is worn, cannot serve the purpose of abrading the polishing pad 6, and must be replaced with a new abrasive dresser 8. That is to say, the life of the abrasive dresser 8 is short. Furthermore, a single abrasive dresser 8 cannot abrade a large number of polishing pads 6 of the polishing disc 4, and hence the efficiency of abrading the polishing disc 4 is reduced.